<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>

        /*css*/
        a:link{
            color: red;
        }
        a:visited{
            color: green;
        }
        a:hover{
            color: red;
        }
        a:focus{
            color:black;
        }
        a:active{
            color: yellow;
        }

        input:focus{
            background-color: blue;
        }

    </style>
</head>
<body>
<p><a href="http://www.baidu.com">click me</a></p>

<form>
    焦点<input>
</form>
</body>
</html>